PROJECT ABSTRACT Wet Age-related Macular Degeneration (AMD) is the leading cause of new blindness among people who are 55 or older. The current standard of care for wet AMD is anti-Vascular Endothelial Growth Factor (VEGF) agents, such as Lucentis, Eylea, and Avastin (used off-label). These anti-VEGF agents inhibit VEGF-mediated angiogenesis, and effectively stop or even reverse the vision loss for most patients. Despite being the best treatment currently available, it has two critical shortcomings: 1) limited near-term vision gain and poor long- term vision maintenance; (2) major cost and treatment burden. First, despite continued treatment, only ~1/3 of the patient gain >3 lines of vision over the first 12 months; after 3-4 years, most patients start losing vision again and eventually dropping to pre-treatment levels. Second, patients must return to the clinic every 1 to 2 months for intravitreal injections ? a specialized, uncomfortable and costly procedure that represents significant treatment burden. Combination therapies, which combine an anti-VEGF agent with disease modifying agents that target other important biomarkers such as PDGF and Ang2, have shown great promise in further improving efficacy and/or reducing treatment burden. However, they require the use of multiple therapeutic agents and sometimes multiple injections, which further increase the cost and treatment burden. In order to address this shortcoming, the ideal next-generation wet AMD treatment should meet the following criteria: a) small in size, in order to achieve high molar dosage and longer duration of efficacy, and facilitate tissue penetration; b) devoid of immunogenicity and immune-stimulatory effects, in order to ensure long-term safety; c) suitable for complex formulation, in order to facilitate future development in slow-release or topical administration technologies; d) most importantly, capable of inhibiting multiple biomarkers with one molecule, in order to improve efficacy without increasing treatment burden and cost. Aptamers are single stranded oligonucleotides that bind to molecular targets in a manner similar to monoclonal antibodies (mAbs). Although aptamers were invented much more recently than mAbs, they have already shown significant potential in wet AMD treatment: Macugen, the first anti-VEGF agent approved by FDA for wet AMD treatment, is an aptamer; Fovista, an anti-PDGF aptamer, is the most advanced combination treatment program; There is also an anti-complement 5 (C5) aptamer (Zimura) currently in Phase II/III trial. The purpose of this SBIR is to develop highly stable, bispecific aptamers that may serve as the optimal combination treatment for wet AMD. To that end, the Aptitude team has accumulated extensive experience in aptamer discovery. We have previously developed the Particle Display method that significantly improves the aptamer performance. We have also developed the method to screen for the optimal linker for a bispecific aptamer. Moreover, we have made further improvement to directly screen for fully modified aptamers that may enable longer duration of efficacy. Our expertise in aptamer discovery is complemented by our collaborators' expertise in wet AMD animal model and clinical trials. If successful, this project has the potential of bringing more efficacious and affordable treatment to wet AMD patients.